The present invention relates generally to machinery for the insertion of electronic components into printed circuit boards and more particularly to an automated machine for the insertion in sequence of a variety of radial leaded components into a circuit board.
The use of printed circuit boards having pre-drilled holes or receptacles for receiving therein the extended leads of electronic components is well established in the electronics industry. The ever growing demand for such circuitry and the highly competitive nature of the industry have created a need for automation in all phases of circuit board assembly. Automated machines have been developed which arrange and retain axial leaded components, e.g. conventional resistors, of one size on continuous belts. These belts are used to feed component insertion machines which select a particular component from an assortment of component belts, form the leads and insert the leads in pre-drilled holes in a printed circuit board. In other applications, the component belts include components in a selected assortment of sizes, retained in a preferred sequence along the belt such that an insertion machine operating with as few as one storage belt can substantially populate a circuit board.
Such machines operating with components stored on continuous belts have been successfully developed for axial leaded components, that is, components having leads which extend substantially coaxially from opposite ends of generally symmetrical component bodies. The symmetry of the stored components simplifies to a degree the problems in developing a machine capable of inserting a variety of axial leaded components.
DIP components, that is those well known, well standardized components in the electronics industry having dual rows of parallel prongs extending from opposite sides of a rectangular body, also, because of their symmetry, lend themselves readily to use with automated machinery. The machines insert the prongs into receptacles mounted to the circuit board.
With both the axial lead and DIP insertion machines, the act of insertion is generally followed by automatic operations which cut off excess lead length from beneath the circuit board. Then the leads are bent to clinch them against the underside of the board so as to fix the components in position prior to subsequent operations, e.g. soldering.
A third type of component, that is the so-called radial leaded components, have leads which extend substantially parallel but not coaxially from the component body. Disc and film capacitors, transistors, induction coils, and the like are produced in abundance in the radial leaded configuration. Twin leads are most common but three and more radial leaded components, e.g. transistors, are available as standard items. However, unlike the DIP and axial leaded components there is little similarity to the physical size and shape of different types of radial leaded components. Accordingly, the difficulty and complexities involved in developing a single machine for the automated insertion of a variety of radial leaded components is substantially increased. Radial leaded components are stored on flat carrier strips where the leads are taped to a stiff paper backing but the component body stands free of the carrier strip. Only the spacings between components on the carrier strip and the spacing of the leads where they are taped have been standardized to a substantial degree. The shape and height of different component types extending beyond the carrier strip differ markedly, making it difficult to have a universal insertion machine for many radial leaded component types.
Problems associated with all insertion machines further intensify as circuit boards, mounted components and the physical spacing between components become smaller. This trend toward compactness of the circuit assemblies requires that the "footprint" of the machine on the circuit board when components are inserted be minimized so that the machine does not damage components already in place. In this regard, it is well understood that accuracy in aligning the component leads with the proper holes in the circuit board prior to insertion is an absolute requisite of every circuit machine if the components are to be inserted without damage.
In the prior art, machines for insertion of radial leaded components in circuit boards have generally gripped the body of the component at the time of aligning the leads to the circuit board holes. Ths method of holding the component body requires that the gripping mechanism be tailored to a particular component type and contour and thus limits the utility of the machine without modification to accomodate mixed components. Examples in the prior art of body-gripping insertion machines for radial leaded components are found in U.S. Pat. Nos. 2,896,208; 3,151,387; 3,257,711; 3,777,350 and 4,051,593.